Conducting polymers, polyaniline (PANI) among them, alone or mixed with conventional polymers, have been successfully applied in batteries, sensors, electro-chromic devices, capacitors, solar cells, corrosion inhibitors, light emitting diodes, metallization, coating for metallic surfaces, etc.
PANI exists in three different forms: leucoemeraldine base (LEB, fully reduced form), emeraldine base (EB, partially oxidized form) and pemigraniline base (PNB, fully oxidized form). Among the different oxidation states of PANI, the emeraldine salt (ES) is the only one that presents electrical conductivity. Nevertheless, the emeraldine base (EB) can be converted to emeraldine salt (ES), and vice-versa, by protonation/de-protonation with acid/base.
PANI nanostructures include nanowires, nano-rods, nanotubes, nanofibers, nano-belts, and nano-ribbons and they can possess advantageous properties, such as high surface areas, good environmental stability and potential applications in molecular wires, chemical sensors, biosensors and artificial muscles. To date, a variety of synthetic approaches, such as seeding polymerization, electrochemical method, interfacial polymerization, hard-template method, soft-template method, and template-free method, have been used for fabrication of PANI micro/nanostructures. There is remaining need in the art, though, for simpler methods and processes for preparing PANI nanostructures, and for improved methods and processes for post-synthesis change of morphology of PANI nanostructures.